Hello, same problem here. I can put my Orange PI Zero in standby with:
systemctl suspend
systemctl suspend
And then it seems to be impossible to wake it up. In my FEX file I added:
wakeup_src_bt = port:PA07<6><default><default><0>
I connected +3.3V to PA07 (GPIO7, AKA the physical pin #12 of the board) with pullup resistor, then I make the OPI Zero sleep and I try to connect PA07 to ground. Nothing happens.